This invention relates to cleaning apparatus, with vapor containment, for use when highly volatile and environmentally hazardous, and also non-environmentally hazardous materials are used as cleaning solvent, e.g., in removing flux from circuit board components and the like.
In the assembly of printed circuit boards, individual components are generally soldered into place using a tin-lead solder and a rosin flux. Following this operation, the assembled board is cleaned to remove all flux. Cleaning solvents in use today which are most efficient for such cleaning are environmentally hazardous. Chlorofluorocarbons and hydrochlorofluorocarbon may be used, the preferred substance being a FREON.TM.. FREON.TM. is an essentially stable, inert, non-flammable, non-explosive, and non-corrosive fluorocarbon product. In actual use, assembled circuit boards are typically lowered into liquid fluorocarbon or fluorocarbon vapor to effect cleaning.
Present systems for cleaning circuit boards are large, open cleaning tanks which have a basin of liquid cleaning agent, such as FREON.TM.. Conventional gas type refrigeration techniques are used to condense the vapor in order to prevent evaporation. A user places components to be cleaned into a carrier basket, which is then lowered into the vapor layer. All flux dissolves in the vapor and/or liquid, and is filtered out. In some present systems, filtered cleaning agent is recirculated and reused. To reduce the amount of vapor released to the environment by the open tanks of the prior art, users must slowly lower and raise the baskets. A typical rate is 11 inches per minute maximum. The vapor escape problem is compounded by vapor layer non-uniformities which occur in large cleaning tanks, i.e., the central region does not readily form and maintain a uniform vapor layer, primarily due to peripheral location of the heat pumps.
In addition to the environmental problems created by commercially available cleaning tanks, use of such tanks causes disruption in the production line. Due to the large size of the tanks, they are generally centrally located in a production facility. Thus, workers must leave work stations to walk over to the large tank. The slow rate at which components must be lowered into and raised out of the tank makes the entire cleaning process slow, resulting in the loss of valuable labor time. To avoid this loss of labor time, beakers of cleaning solvent are often placed at each work station. There are obvious disadvantages to such an arrangement, including vapor loss to the environment, and potential spills in the work environment. Thus, there is a need for an efficient, bench-top cleaning apparatus for use at a work station.
Accordingly, it is an object of the present invention to provide an improved cleaning apparatus with vapor containment.
It is another object of the invention to provide an efficient, environmentally safe bench-top cleaning apparatus for use in cleaning circuit boards.